Influence of Flow Stress and Friction Upon Metal Flow in Upset Forging of Rings and Cylinders

1972 ◽  
Vol 94 (3) ◽  
pp. 775-782 ◽  
Author(s):  
C. H. Lee ◽  
T. Altan
Keyword(s):  
Flow Stress ◽  
Velocity Field ◽  
Strain Rate ◽  
Calibration Curve ◽  
Upper Bound ◽  
Metal Flow ◽  
Computer Programs ◽  
Ring Test ◽  
Stress Distributions ◽  
Upset Forging

An upper-bound velocity field that considers bulging has been applied to cylinder and ring upsetting. Computer programs have been developed to (a) determine strain, strain rate, velocity, and flow-stress distributions, and (b) predict load and bulge profile at various reductions by simulating the upsetting process. The calibration curve for a 6:3:2 ring, the load-displacement curves for ring and cylinder upsetting, and flow stress from the ring test have been predicted. The experimental results, with annealed 1100 Aluminum samples, agree well with theory at the lower and practical range of friction, but they show some disagreement at high friction.

Plane-Strain Plastic Flow of Strain-Rate Sensitive Materials

1974 ◽  
Vol 96 (3) ◽  
pp. 238-240 ◽  
Author(s):  
R. G. Fenton ◽  
B. Durai Swamy
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Plane Strain ◽  
Slip Line ◽  
Metal Flow ◽  
Stress Distributions ◽  
Line Field ◽  
Slip Line Field ◽  
Flow Problems ◽  
Iterative Calculation

A numerical method based on the modified Hencky and Geiringer equations is described for solving plane-strain metal flow problems of strain-rate sensitive materials. The slip-line field and flow-stress distributions are determined simultaneously using an iterative calculation.

SIMULATION OF MULTI-PASS HOT ROLLING BY A MIXED ANALYTICAL-NUMERICAL METHOD

2011 ◽  
Vol 03 (03) ◽  
pp. 469-489 ◽  
Author(s):  
JINLING ZHANG ◽  
ZHENSHAN CUI
Keyword(s):  
Mathematical Model ◽  
Flow Stress ◽  
Strain Rate ◽  
Numerical Method ◽  
Hot Rolling ◽  
High Efficiency ◽  
Rolling Force ◽  
Metal Flow ◽  
Fem Simulation ◽  
Rolling Process

A mathematical model integrating analytical method with numerical method was established to simulate the multi-pass plate hot rolling process, predicting its strain, strain rate, stress and temperature. Firstly, a temperature analytical model was derived through series function solution, the coefficients in which for successive processes were smoothly transformed from the former process to the latter. Therefore, the continuous computation of temperature for multi-operation and multi-pass was accomplished. Secondly, kinematically-admissible velocity function was developed in Eulerian coordinate system according to the principle of volume constancy and characteristics of metal flow during rolling with undetermined coefficients — which were eventually solved by Markov variational principle. Thirdly, strain rate was calculated through geometric equations and the difference-equations for solving strain and a subsequent recurrent solution were established. Fourthly, rolling force was calculated on the base of Orowan equilibrium equation, considering the contribution to flow stress of strain, strain rate and temperature, rather than taking the flow stress as a constant. Consequently, the thermo-mechanics and deformation variables are iteratively solved. This model was employed in the simulation of an industrial seven-pass plate hot rolling schedule. The comparisons of calculated results with the measured ones and the FEM simulation results indicate that this mathematical model is able to reasonably represent the evolutions of various variables during hot rolling so it can be used in the analysis of practical rolling. Above all, the greatest advantage of the presented is the high efficiency. It costs only 12 seconds to simulate a seven-pass schedule, more efficient than any other numerical methods.

A Three-Dimensional Upper Bound Elemental Technique for Forging Analysis

1996 ◽  
Vol 210 (4) ◽  
pp. 353-359 ◽  
Author(s):  
R S Lee ◽  
C T Kwan
Keyword(s):  
Velocity Field ◽  
Upper Bound ◽  
Metal Flow ◽  
Three Dimensional ◽  
Velocity Fields ◽  
Connecting Rod ◽  
Total Energy Consumption ◽  
Pure Lead ◽  
Forming Load ◽  
Theoretical Predictions

In this paper, two kinematically admissible velocity fields are derived for the proposed three-dimensional arbitrarily triangular and trapezoidal prismatic upper bound elemental technique (UBET) elements. These elements are applied to the portions between the circular shaped part and the straight rod part with three-dimensional metal flow in connecting rod forging, and then the capability of the proposed elements are shown. From the derived velocity fields, the upper bound loads on the upper die and the velocity field are determined by minimizing the total energy consumption with respect to some chosen parameters. Experiments with connecting rod forging were carried out with commercial pure lead billets at ambient temperature. The theoretical predictions of the forming load is in good agreement with the experimental results. It is shown that the proposed UBET elements in this work can effectively be used for the prediction of the forming load and velocity field in connecting rod forging.

On the Extrusion in Superplastic Conditions

1975 ◽  
Vol 97 (3) ◽  
pp. 1131-1135 ◽  
Author(s):  
A. Alto ◽  
G. Giorleo
Keyword(s):  
Velocity Field ◽  
Constitutive Equation ◽  
Strain Rate ◽  
Experimental Evidence ◽  
Upper Bound ◽  
Extrusion Pressure ◽  
Slab Method ◽  
Conical Die ◽  
Strain Rate Field ◽  
Superplastic Condition

In this paper the range within which the slab method is accurate enough to calculate the extrusion pressure in superplastic condition has been determined. A realistic velocity field, supported by experimental evidence, has been adopted. A strain rate field has been evaluated and an appropriate constitutive equation has been introduced. The slab method and the upper bound approach, here developed, have then been used to study the superplastic extrusion through a conical die. A comparison of the two solutions thus obtained has been carried out. It has been found that in any case the curves obtained using the slab method run higher than those obtained using the upper-bound approach. The analysis developed may be used to determine the range within the slab method is accurate enough for engineering purposes.

Analysis and Technology in Metal Forming

1989 ◽  
Author(s):  
Shiro Kobayashi ◽  
Soo-Ik Oh ◽  
Taylan Altan
Keyword(s):  
Heat Transfer ◽  
Plastic Deformation ◽  
Flow Stress ◽  
Velocity Field ◽  
Metal Forming ◽  
Metal Flow ◽  
Die Design ◽  
Flow Forming ◽  
Part Geometry ◽  
Formed Part

The design, control, and optimization of forming processes require (1) analytical knowledge regarding metal flow, stresses, and heat transfer, as well as (2) technological information related to lubrication, heating and cooling techniques, material handling, die design and manufacture, and forming equipment. The purpose of using analysis in metal forming is to investigate the mechanics of plastic deformation processes, with the following major objectives. • Establishing the kinematic relationships (shape, velocities, strain-rates, and strains) between the undeformed part (billet, blank, or preform) and the deformed part (product); i.e., predicting metal flow during the forming operation. This objective includes the prediction of temperatures and heat transfer, since these variables greatly influence local metal-flow conditions. • Establishing the limits of formability or producibility; i.e., determining whether it is possible to perform the forming operation without causing any surface or internal defects (cracks or folds) in the deforming material. • Predicting the stresses, the forces, and the energy necessary to carry out the forming operation. This information is necessary for tool design and for selecting the appropriate equipment, with adequate force and energy capabilities, to perform the forming operation. Thus, the mechanics of deformation provides the means for determining how the metal flows, how the desired geometry can be obtained by plastic deformation, and what the expected mechanical properties of the produced part are. For understanding the variables of a metal-forming process, it is best to consider the process as a system, as illustrated in Fig. 2.1 in Chap. 2. The interaction of most significant variables in metal forming are shown, in a simplified manner, in Fig. 3.1. It is seen that for a given billet or blank material and part geometry, the speed of deformation influences strain-rate and flow stress. Deformation speed, part geometry, and die temperature influence the temperature distribution in the formed part. Finally, flow stress, friction, and part geometry determine metal flow, forming load, and forming energy. In steady-state flow (kinematically), the velocity field remains unchanged, as is the case in the extrusion process; in nonsteadystate flow, the velocity field changes continuously with time, as is the case in upset forging.

Flow Stress of Metals and Its Application in Metal Forming Analyses

1973 ◽  
Vol 95 (4) ◽  
pp. 1009-1019 ◽  
Author(s):  
T. Altan ◽  
F. W. Boulger
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Metal Forming ◽  
Cold Extrusion ◽  
Rate Dependency ◽  
Tool Steels ◽  
Forming Load ◽  
Closed Die Forging ◽  
Upset Forging ◽  
Flow Stress Data

Forming load and energy can be determined if the flow stress of the deforming, material is known at the temperature and strain-rate conditions existing during the process. In this study domestic and foreign melalforming articles were reviewed and the available flow stress data have been presented for selected carbon, stainless, and tool steels; aluminum, copper, and titanium alloys; magnesium, uranium, zircaloy, molybdenum, tungsten, tantalum, and niobium. Whenever possible, data are presented by calculating and tabulating coefficients K and n to express strain hardening (flow stress σ¯ = Kε¯n), and C and m to express strain-rate dependency (σ¯=Cε¯˙m). Examples are given to illustrate the use of flow-stress data with simple formulas in predicting pressures in upset forging, closed-die forging, and cold extrusion.

On the Velocity and the Strain Rate Field in Unlubricated Direct and Indirect Axisymmetric Extrusion of Al

2014 ◽  
Vol 611-612 ◽  
pp. 1013-1020
Author(s):  
Sepinood Torabzadeh Khorasani ◽  
Henry Valberg
Keyword(s):  
Velocity Field ◽  
Strain Rate ◽  
Deformation Zone ◽  
Good Accuracy ◽  
Fe Simulation ◽  
Metal Flow ◽  
Fe Analysis ◽  
Extrusion Die ◽  
Strain Rate Field ◽  
Good Agreement

The velocity and strain rate fields in the primary deformation zone ahead of the extrusion die opening are investigated by theory and FE-simulation for direct and indirect Al extrusion. The metal flow obtained in the FEM-models of extrusion is compared with the flow recorded in previous experiments and it is shown that the FE-analysis mimics real metal flow with good accuracy. The velocity and the strain rate fields computed by FEA (using DEFORM® 2D) are described and comparison is made with the idealized spherical velocity field of Avitzur, to see if there is good agreement between the results from theory and FEA, and the correlation between the results from the two is discussed. Moreover, a clear difference in metal flow is confirmed between the two processes direct (FwE) and indirect extrusion (BwE).

An Approximate Method for Predicting Metal Flow in Forging and Extrusion Operations

1980 ◽  
Vol 194 (1) ◽  
pp. 9-15 ◽  
Author(s):  
J. N. Thornton ◽  
A. N. Bramley
Keyword(s):  
Flow Stress ◽  
Strain Hardening ◽  
Approximate Method ◽  
Upper Bound ◽  
Reasonable Agreement ◽  
Cold Working ◽  
Metal Flow ◽  
Hot Forging ◽  
Experimental Results ◽  
Constant Flow

A method of metal flow, load and strain prediction in forming operations is presented. Based on the upper-bound elemental technique, it is applied to hot forging operations where a constant flow stress can be assumed and also to cold working of aluminium and steel where the effects of strain hardening are taken into account. The predictions were found to be in reasonable agreement with experimental results.

An Analysis of Three-Dimensional Upset Forging of Regular Polygonal Blocks by Using the Upper-Bound Method

1987 ◽  
Vol 109 (2) ◽  
pp. 155-160 ◽  
Author(s):  
D. Y. Yang ◽  
J. H. Kim
Keyword(s):  
Velocity Field ◽  
Upper Bound ◽  
Pure Copper ◽  
Three Dimensional ◽  
Total Power ◽  
Total Power Consumption ◽  
Upset Forging ◽  
Theoretical Predictions ◽  
Forging Load ◽  
Good Agreement

A simple kinematically admissible velocity field for three-dimensional deformation in upset forging of regular polygonal blocks is proposed which takes into account the sidewise spread as well as the bulging along thickness. From the proposed velocity field the upper-bound load and the deformed configuration are determined by minimizing the total power consumption with respect to three chosen parameters. Experiments are carried out with annealed commercially pure copper at room temperature for different thicknesses, billet shapes and lubrication conditions. The theoretical predictions both in the forging load and the deformed configuration are in good agreement with the experimental results. It is thus shown that the velocity field proposed in this work can be conveniently used for the prediction of the forging load and deformation in the upset forging of regular polygonal blocks.

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